Method for controlling yaw and transversal dynamics in a road vehicle

ABSTRACT

For the purpose of controlling the yaw dynamics and lateral dynamics in a road vehicle with electrically controlled four-wheel steering, in the case of which the setting of the front axle steer angle δ v  and of the rear axle steer angle δ h  is performed by means of mutually decoupled control loops, a desired value δ vsoll  for the lateral force S v  to be built up at the front axle is determined in the control loop assigned to the front axle and, for this desired value S vsoll , the value of the slip angle, linked to the desired value S vsoll , is determined as desired value α vsoll  from an S v (α v ) characteristic representing the dependence of the lateral force S v , to be built up at the front axle, on the slip angle α v . In the control loop assigned to the rear axle, a desired value S hsoll  for the lateral force S h  to be built up at the rear axle is determined in a control process in accordance with a controller law of the form 
         S   hsoll     =           l   v     ·   m   ·     v   x       L     ·     [       Ψ   .     -     β   hsoll     +       k   1     ·     (       β   h     -   β   ⁢     -   hsoll       )         ]           
 
and, for this desired value S hsoll , the value of the slip angle, linked to the desired value S hsoll , is determined as desired value α hsoll  from an S h (α h ) characteristic. These desired values α vsoll  and α hsoll  are used to determine the desired values δ vsoll  and δ hsoll  of the steer angle, taking account of an estimated value of the sideslip angle β at the center of gravity of the vehicle, the position of the center of gravity and measured or estimated values of the yaw velocity {dot over (Ψ)} and of the longitudinal speed v x  of the vehicle.

BACKGROUND AND SUMMARY OF THE INVENTION

This application claims the priority of Application No. 100 397 82.4,filed Aug. 16, 2000, in Germany, the disclosure of which is expresslyincorporated by reference herein.

The invention relates to a method and apparatus for controlling the yawdynamics and lateral dynamics in a road vehicle having one steeringdevice each for the front axle and for the rear axle, and havingelectrically drivable δ_(v) and δ_(h) steer-angle actuators. Theseactuators are assigned to the axles individually and can each be drivenvia a controller. These controllers generate from desired/actual valuecomparisons of variables which are characteristic of the yaw-dynamic andthe lateral-dynamic behavior of the vehicle (e.g., the yaw velocity {dotover (Ψ)} and a sideslip angle β) drive signals required for correctingthe controlled variables, i.e., for the steer angle actuators. Controlloops, provided for setting the steer angles δ_(v) and δ_(h), aredecoupled from one another. The desired value prescription signals,required for the two control loops, for the control parameters aregenerated by means of a reference model, implemented by an electroniccomputer, from processing at least one output signal, representing thedriver's wish, from a steering element position sensor and a sensoroutput signal characteristic of the operating state of the vehicle, forexample a speed sensor.

In vehicles that are equipped with steer-angle actuators that can bedriven independently of one another for front axle steering and rearaxle steering, it is possible in principle to obtain “extreme” vehiclemovements that cannot occur in the case of a normal vehicle which can besteered only via the front wheels. For example, a sideslip of thevehicle, that is to say a movement of the vehicle obliquely relative tothe vehicle longitudinal axis, is possible without the vehicle yawing(e.g., by virtue of the fact that the front axle steering and the rearaxle steering are set to the same steer angle with reference to thevehicle longitudinal axis). It is also possible to obtain a yawing, thatis to say a rotary movement of the vehicle about its vertical axis,without the vehicle executing a slipping movement.

The use of such vehicle movements, which can be obtained only withtwo-axle steering, should be reserved for reasons of safety for suchdriving situations in which the driver consciously adopts such anunaccustomed vehicle behavior, for example, maneuvering in a very tightspace. Such vehicle movements should not be used in the “normal”operation of the vehicle, corresponding to the statistically dominantdriving situations, for which operation the driver “customarily” expectsa reaction of the vehicle corresponding to the driver's wish.

It is, therefore, an object of the invention to specify a method of thetype disclosed herein, which upon actuation of a steering elementprovided for setting a driver's wish, for example a steering wheel orjoystick, leads to a vehicle reaction which is largely analogous to thatof a vehicle which has only front axle steering, but yet permitsimproved utilization of the lateral guiding forces that can be built upby the two steer-angle actuators.

This object is achieved in the case of a method of the type disclosedherein by the overall combination of controlling the yaw dynamics andlateral dynamics in a road vehicle having one steering device each forthe front axle and for the rear axle, and having electrically drivableδ_(v) and δ_(h) steer angle actuators, as regards the basic idea, withdetermining the desired value S_(vsoll) of the lateral force to be builtup at the front axle is determined in a control process in accordancewith a controller law of the form$S_{vsoll} = {\frac{l_{h} \cdot m \cdot v_{x}}{L} \cdot \left\lbrack {\overset{.}{\Psi} - {\overset{.}{\beta}}_{vsoll} + {k_{2} \cdot \left( {\beta_{v} - \beta -_{vsoll}} \right)}} \right\rbrack}$or the desired value S_(vsoll) of the lateral force to be built up atthe front axle is determined in a control process in accordance with acontroller law of the form$S_{vsoll} = {\frac{l_{h} \cdot m \cdot a_{y}}{L} + {\frac{J_{z}}{L} \cdot {\left\lbrack {{\overset{.}{\Psi}}_{soll} + {k_{3} \cdot \left( {\overset{.}{\Psi} - {\overset{.}{\Psi}}_{soll}} \right)}} \right\rbrack.}}}$

In this case, the type of determination of a desired value of thelateral force at the front wheels provided in accordance with thedesired value S_(vsoll) of the lateral force to be built up at the frontaxle corresponds to a sideslip angle control at the front axle in theway provided in general for determining the desired value of the lateralforce at the rear axle, while the type of determination of a desiredvalue of the lateral guiding force at the front axle corresponds to acontrol of yaw velocity via the steer angle control loop assigned to thefront axle. The approximate determination of the method of determiningthe desired values of the slip angle of the front wheels and the rearwheels of the vehicle is sufficient in the majority of statisticallysignificant driving situations to be able to carry out a determinationof steer angle for the front and rear wheels of the vehicle that isadequate for the situation.

In the case of a control device for a road vehicle having one steeringdevice each for the front axle and for the rear axle and havingelectrically drivable steer angle actuators, assigned to said axlesindividually, for two mutually decoupled control loops which aresuitable for implementing the control of lateral force based on yawcomputation, the method of a lateral acceleration sensor which directlydetects the lateral acceleration active at the center of gravity of thevehicle is particularly expedient.

Taking account of the vehicle geometry, it is also possible for thisdevice to provide two lateral acceleration sensors whose spacing fromone another measured in the longitudinal direction of the vehicle may beas large as possible.

Both owing to an ability to switch over the control device to variousdefined control modes, and by means of a specific selection betweendifferent reference model variants of the vehicle which are provided forgenerating the prescribed desired values for the front axle and rearaxle steer angles δ_(v) and δ_(h) and implemented by a computer, it ispossible to set the vehicle to correspondingly different types of itsresponse behavior to an actuation, acting as an expression of a specificdriver's wish, of a steering element, i.e., the vehicle type (sports caror heavy limousine) can be selected, which corresponds to the desireddriving behavior of the vehicle. The control modes described herein mayalso be used whenever the rear axle steering is implemented by virtue ofthe fact that the rear wheel brakes can be driven individually todevelop defined braking forces, as a result of which they canspecifically influence the yaw behavior of the vehicle via the rearwheels even without a steer-angle actuator for the rear axle.

The automatic switchover of the control device to a control mode withthe yaw velocity as a controlled variable in which the vehicle is movingin the extreme range of lateral dynamics, i.e., the lateral forces mayno longer be increased by enlarging slip angles, results in the factthat the vehicle still remains capable of being effectively controlledeven an extreme range and/or in the event of failure of the rear axlesteering, and a high measure of safety is achieved to this extent.

A significant improvement in the quality of control is achieved by meansof disturbance estimators assigned to the controlled variables,preferably ones whose design model corresponds to that of the controllerfor the observed controlled variable, since, by contrast with acontroller with an integral-action component, it is not the controlerror that is integrated, but the error between measurement andestimate, which can then be used to compensate disturbances.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematically simplified block diagram of a deviceaccording to an embodiment of the invention for the control of lateraldynamics on a road vehicle with front axle steering and rear axlesteering, and

FIG. 2 shows a lateral force/slip angle diagram for illustration of thefunctioning of the control device in accordance with FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A lateral dynamics control device 10, in FIG. 1, for a four-wheel driveroad vehicle 11. Both the front wheels 12 and 13 and the rear wheels 14and 16 of the vehicle 11 can be steered, and an electrically drivablesteer angle actuator 17 or 18 may be provided for setting steer anglesδ_(v) of the front wheels 12 and 13 and for setting steer angles δ_(h)of the rear wheels 14 and 16, respectively. The aim is to achieve asteering behavior which permits the vehicle to be guided by the driverin an effectively controllable fashion.

For the purpose of explanation, it may be assumed for the vehicle 11that the front axle steer angle actuator 17 effects a “common” settingof the steer angles δ_(vl) and δ_(vr) for the two front wheels in themanner of trapeze steering. Additionally, the same also holds for therear axle steer angle actuator 18. For the purpose of a simplifying“single-track” model of the vehicle, the front wheel steer angles δ_(vl)and δ_(vr) can be described by a single front axle steer angle δ_(v),and the rear wheel steer angles δ_(hl) and δ_(hr) can be described by acommon “mean” rear axle angle δ_(h).

The steer angle actuators 17 and 18 can be implemented aselectrohydraulic or as electromechanical actuators which can be drivenby electric signals, which represent desired values δ_(vsoll) andδ_(hsoll) of the front axle steer angle δ_(v) and the rear axle steerangle δ_(h), seen in the single-track model of the vehicle 11, in orderto set the relevant desired values.

These desired value signals for the front axle steer angle δ_(v) and therear axle steer angle δ_(h) are generated by controllers 19, 21, and 22which operate in control loops decoupled from one another, and generatedrive signals characteristic of desired values for the steer angleactuators 17 and 18 from desired/actual value comparisons of variablescharacteristic of the lateral-dynamic behavior of the vehicle 11,specifically the yaw angular velocity {dot over (Ψ)} at the center ofgravity 23 of the vehicle 11, the sideslip angle β_(v) in the region ofthe front axle 24 of the vehicle, and the sideslip angle β_(h) in theregion of the rear axle 26 of the vehicle 11.

In order to convert the driver's wish for a lateral-dynamic behavior heor she expects of the vehicle 11, and which the driver may indicate byactuating a steering element 27, e.g., a “conventional” steering wheelas illustrated or a joystick, provision is made of a reference model 28.This model may be implemented by an electronic computer to which thereis fed at a first input 29, the “driver's wish input,” an electricoutput signal, characteristic of a steer angle δ_(F), of a steeringelement position sensor 31 which corresponds to a steering behavior ofthe vehicle 11 desired by the driver. At a second input 32, a “speedinput,” the reference model 28 may be fed an electric state signal whichis a measure of the longitudinal speed v_(x) of the real vehicle.

The reference model 28 outputs at a first output 33 an electric outputsignal which is a measure of a desired value {dot over (Ψ)}_(soll) ofthe yaw angular velocity of the real vehicle about its vertical axispassing through the center of gravity 23.

At a second output 34, the reference model 28 outputs an electric outputsignal which, in the event of cornering, is a measure of the desiredvalue β_(vsoll) of the sideslip angle of the vehicle in the region ofits front axle 24. At a third output 36, it outputs an electric outputsignal which is a measure of the desired value β_(hsoll) of the sideslipangle of the real vehicle 11 at the rear axle 26 of the vehicle.

The generation of these desired values, whose input determines thereaction behavior of the vehicle to an actuation of the steering wheel27—setting of the steer angle δ_(F)—is expediently done so as to producea lateral-dynamic behavior of the vehicle 11 that is “understandable,”i.e., effectively manageable, to the driver. The reference model 28 maybe designed so as to produce a “neutral” cornering behavior to whichidentical slip angles α_(v) and α_(h) at the front axle 24 and the rearaxle 26 correspond; however, it is also possible for the reference model28 to be designed so as to produce a cornering behavior of the vehiclewhich is easy to oversteer and approximates that of a sports vehicle, orelse to achieve an oversteering behavior such as may be characteristicof front-wheel-drive vehicles.

Actual value signals suitable for comparison with the {dot over(Ψ)}_(soll), β_(vsoll), and β_(hsoll) value signals are generated by avehicle model 37, which is also implemented by an electronic computerand outputs at a first output 38, from processing-measured,operationally characteristic variables and vehicle-specific data, anelectric output signal which is a measure of the actual value {dot over(Ψ)}_(ist) of the yaw angular velocity of the vehicle 11 about itsvertical axis. The vehicle model 37 also outputs at a second output 39an electric output signal which is a measure of the actual valueβ_(vist) of the sideslip angle of the front axle 24, and further outputsat a third output 41 an electric output signal which is a measure of theactual value β_(hist) of the sideslip angle β_(h) at the rear axle 26 ofthe real vehicle 11.

Variable data suitable for generating the actual value output signals ofthe vehicle model 37, i.e., ones which must be detected continuouslyduring driving operation, and “vehicle-specific data,” i.e., ones whichare permanently prescribed by the vehicle or can be detected by a singlemeasurement and can then be regarded as constant at least for arelatively long time interval, are as follows in the case of a selectedexemplary embodiment: the output signals of wheel speed sensors 42 ₁ to42 ₄ individually assigned to the vehicle wheels 12, 13, 14, and 16,which permit accurate determination of the longitudinal speed v_(x) ofthe vehicle; the output signals of an electronic or electromechanicalfront axle steer angle position sensor 43 assigned to the front axlesteer angle actuator 17, and of a steering element position sensor 44assigned to the rear axle steer angle actuator 18; the output signal ofa yaw velocity ({dot over (Ψ)}) sensor 46 as a measure of the yawvelocity {dot over (Ψ)} about the vertical axis of the vehicle passingthrough the center of gravity 23 of the same, the output signal of alateral acceleration (a_(y)) sensor 47 as a measure of the lateralacceleration ay acting at the center of gravity 23 of the vehicle 11perpendicular to the vehicle longitudinal direction, the x-direction;and if appropriate, the output signal of a lateral acceleration sensor48, expediently arranged in the vicinity of the front axle 24, and/orthe output signal of a lateral acceleration (a_(yh)) sensor 49 arrangedmore in the vicinity of the rear axle 26 as a measure of a lateralacceleration acting in the lateral direction on the vehicle at adistance from its center of gravity 23.

Stored in the vehicle model 37 as “vehicle-specific” data which aresuitable in conjunction with the above-named variable data fordetermining the actual values {dot over (Ψ)}_(ist), β_(vist) andβ_(hist) are the wheelbase L of the vehicle and, if appropriate, thewheel track of the front and rear axles as fixed value(s). Further,variables subjected at most to slight variations, which can be correctedif required by intermittent measurement or estimation, are the vehiclemass m, the distance l_(v) of the center of gravity 23 from the frontaxle 24, or l_(h) of the center of gravity 23 from the rear axle 26, theyaw moment of inertia J_(I) of the vehicle 11 about its vertical axis,and tire characteristics. These variables may reproduce the relationshipbetween the lateral forces S_(v) and S_(h), which can be built up bysteering actuation at the front axle and the rear axle, as a function ofthe respective slip angles α_(v) and α_(h).

In order to explain the processing of these variables by the modelcomputer 37, reference is made below to a simplified linearizedsingle-track model of a road vehicle, in which the steer angles δ_(v)and δ_(h) at the front axle 24 and the rear axle 26, respectively, aregiven by the following relationships: $\begin{matrix}{{\delta_{v} = {{- \beta} + \frac{l_{v} \cdot \overset{.}{\Psi}}{v_{x}} + a_{v}}}{and}} & (1) \\{\delta_{h} = {{- \beta} - \frac{l_{h} \cdot \overset{.}{\Psi}}{v_{x}} + {a_{h}.}}} & (2)\end{matrix}$

In the linearized single-track model, i.e., one regarded for smallvalues of the steer angles δ_(v) and δ_(h) or around 10°, selected forthe purpose of explanation, the sideslip angle β at the center ofgravity of the vehicle 11 is given to a good approximation by therelationship $\begin{matrix}{\beta = {- \frac{v_{y}}{v_{x}}}} & (3)\end{matrix}$in which v_(y) denotes the velocity component of the vehicle producedduring cornering perpendicular to the longitudinal velocity componentv_(x) of the vehicle velocity v_(F) which is determined by the vectorsum of these two velocity components.

The lateral velocity component v_(y) may be “measured,” or at leastapproximately determined, from an integration of the lateralacceleration a_(y) acting at the center of gravity of the vehicle,and/or be estimated from the wheel speeds, the set steer angles δ_(v)and δ_(h), and the geometrical dimensions of the vehicle.

Furthermore, the sideslip angles β_(v) and β_(h) at the front axle orthe rear axle, respectively, are linked to the sideslip angle β at thecenter of gravity of the vehicle by the relationships $\begin{matrix}{{\beta_{v} = {\beta - \frac{J_{z} \cdot \overset{.}{\Psi}}{l_{h} \cdot m \cdot v_{x}}}}{and}} & (4) \\{\beta_{h} = {\beta + {\frac{J_{z} \cdot \overset{.}{\Psi}}{l_{v} \cdot m \cdot v_{x}}.}}} & (5)\end{matrix}$

The controller 19 provided for driving the front axle steer angleactuator 17 is designed as a yaw velocity controller which uses acontroller law in the form of $\begin{matrix}{S_{vsoll} = {\frac{l_{h} \cdot m \cdot a_{y}}{L} + {\frac{J_{z}}{L} \cdot \left\lbrack {{\overset{¨}{\Psi}}_{soll} - {k \cdot \left( {\overset{.}{\Psi} - {\overset{.}{\Psi}}_{soll}} \right)}} \right\rbrack}}} & (6)\end{matrix}$to determine a desired value S_(vsoll) of the lateral force which is afunction S(α_(v)) of the slip angle α_(v) at the front axle.

Corresponding to this desired value S_(vsoll), which is determined bythe yaw velocity control and by the relationship $\begin{matrix}{{S_{vsoll} = {\frac{l_{h} \cdot m \cdot a_{y}}{L} + \frac{J_{1} \cdot {\overset{¨}{\Psi}}_{soll}}{L}}}\quad} & \left( 6^{\prime} \right)\end{matrix}$in the event of a vanishing system deviation e ( where e={umlaut over(Ψ)}−{umlaut over (Ψ)}_(soll)=0), is the requirement, holding for stablecornering of the vehicle and expressed in general by the relationshipJ ₁·{umlaut over (Ψ)}=S _(v)·1_(v)−1_(h) ·S _(h)  (7)for balancing the moments about the vertical axis of the vehicle 11 whenthe lateral force S_(h) occurring at the rear axle 26 of the vehicle 11is eliminated in this relationship (7) in accordance with therelationshipm·a _(y) =S _(v) +S _(h)  (8).

Because of the dependence, illustrated qualitatively in FIG. 2, of thelateral forces, which can be determined, mathematically as it were, inaccordance with the relationship (6′), on the slip angles α to be set bythe steering actuation, in accordance with the relationship$\begin{matrix}{\delta_{vsoll} = {{- \beta} + \frac{l_{v} \cdot \overset{.}{\Psi}}{v_{x}} + a_{vsoll}}} & \left( 1^{\prime} \right)\end{matrix}$there is linked to each by the {dot over (Ψ)} control in accordance withthe relationships (6) and (6′), respectively, a desired value α_(vsoll)of the slip angle which is to be used in accordance with therelationship (1) in the determination of the desired value δ_(vsoll) forthe manipulated variable δ_(v) and desired value α_(vsoll) of the slipangle α_(v). The dependence of the lateral force S on the slip angle αis either stored in tabular form in the {dot over (Ψ)} controller 19,which is implemented for its part as a computer and determines thedesired value δ_(vsoll) for the front axle steer angle δ in accordancewith the relationship (1′), or implemented by a control algorithm whichcan be evaluated by the computer. In the case of the exemplaryembodiment selected for explanation, the desired value α_(vsoll) of theslip angle is determined for the purpose of a linear approximation inaccordance with a relationship of the form $\begin{matrix}{{a_{vsoll} = \frac{S_{vsoll}}{C_{v}}},} & (9)\end{matrix}$in which C_(v) denotes a slip stiffness characteristic of the tire.Values of this slip stiffness can be taken from manufacturers' data orestimated or determined by suitable experiments and/or adaptivemeasurement methods. The approximation in accordance with therelationship (9) constitutes a sufficiently accurate approximation, atleast for small slip angles (up to 10°) as may be gathered directly fromthe S(α) characteristic curve 51 of the diagram shown in FIG. 2.

The {umlaut over (Ψ)}_(soll) value required for the evaluation of therelationship (6) or (6′) by the {dot over (Ψ)} controller 19 isgenerated by the reference model 12—by differentiating the {dot over(Ψ)}_(soll) output signal with respect to time—and is fed directly tothe controller 19, as illustrated schematically by a {umlaut over(105)}_(soll) signal path 53.

The system deviation e is determined at the {dot over (Ψ)} referencepoint 52 as the difference between the {dot over (Ψ)}_(ist) value signaloutput by the real vehicle model 37 and the {dot over (Ψ)}_(soll) valuesignal output by the reference model 28, and processed in the controllerin accordance with the relationship (6) with the aid of a controllergain k, freely selectable in principle, of the {dot over (Ψ)} controller19.

The inputs, further required by the {dot over (Ψ)} controller, of thevariables l_(h) ·m·a_(y)/L, the ratio J₂/L, the sideslip angle β at thecenter of gravity of the vehicle, and the variable l_(v)·{dot over(Ψ)}/v_(x) are generated by the real vehicle model 37 and fed “directly”to the controller 19. The signal paths required for this purpose arerepresented only by a single signal path arrow 54 in FIG. 1, for thesake of simplicity.

The controller 22 provided for driving the rear axle steer angleactuator 18 is designed as a sideslip angle (β_(h)) controller, whichuses a controller law of the form $\begin{matrix}{S_{hsoll} = {\frac{l_{v} \cdot m \cdot v_{x}}{L} \cdot \left\lbrack {\overset{.}{\Psi} - {\overset{.}{\beta}}_{hsoll} + {k_{1}\left( {\beta_{hist} - \beta_{hsoll}} \right)}} \right\rbrack}} & (10)\end{matrix}$to determine a desired value for the lateral force S(α_(h)) to be builtup at the rear axle 26 of the vehicle 11 by actuating the steering. Thisdesired value that may be determined by the β_(h) control is given inthe case of a vanishing system deviation (β_(hist)−β_(hsoll)=0) by therelationship $\begin{matrix}{S_{hsoll} = {\frac{l_{v} \cdot m \cdot v_{x}}{L} \cdot {\left\lbrack {\overset{.}{\Psi} - {\overset{.}{\beta}}_{hsoll}} \right\rbrack.}}} & \left( 10^{\prime} \right)\end{matrix}$

The starting point for designing the controller is the plausibleassumption that the temporal change β_(h) in the sideslip angle at therear axle 26 of the vehicle 11 is proportional to the difference betweenthe sideslip angle actual value β_(hist) and the desired valueβ_(hsoll).

By being differentiated with respect to time, the relationship (5) forthe sideslip angle β_(h) at the rear axle of the vehicle yields therelationship $\begin{matrix}{{\overset{.}{\beta}}_{h} = {\overset{.}{\beta} + \frac{J_{z} \cdot \overset{¨}{\Psi}}{l_{v} \cdot m \cdot v_{x}}}} & \left( 5^{\prime} \right)\end{matrix}$which, taking account of the relationship (3), assumes the followingform on the assumption that the longitudinal speed component v_(x) ofthe vehicle can be regarded as constant: $\begin{matrix}{{\overset{.}{\beta}}_{h} = {{- \frac{{\overset{.}{v}}_{y}}{v_{x}}} + \frac{J_{z} \cdot \overset{¨}{\Psi}}{l_{v} \cdot m \cdot v_{x}}}} & \left( 5^{''} \right)\end{matrix}$

It follows directly from the requirement for balancing the lateralforces at the vehicle during cornering, written in the form$\begin{matrix}{{mv}_{y} = {S_{v} + S_{h} - {m \cdot v_{x} \cdot \overset{.}{\Psi}}}} & (11)\end{matrix}$that $\begin{matrix}{{\overset{.}{v}}_{y} = {\frac{S_{v} + S_{h}}{m} - {v_{x} \cdot {\overset{.}{\Psi}.}}}} & \left( 11^{\prime} \right)\end{matrix}$

Substituting the relationship (11′) in the relationship (5″) yields therelationship $\begin{matrix}{{\overset{.}{\beta}}_{h} = {{- \frac{S_{v} + S_{h}}{m \cdot v_{x}}} + \overset{.}{\Psi} + {\frac{J_{z} \cdot \overset{.}{\Psi}}{l_{v} \cdot m \cdot v_{x}}.}}} & (12)\end{matrix}$

If the front axle lateral force S_(v) is eliminated from thisrelationship (12) with the aid of the relationship (7) expressing therequirement for balancing the moments in the case of the vehicle, thefollowing relationship is yielded for the temporal change {dot over(β)}_(h), in the sideslip angle at the rear axle 26 $\begin{matrix}{{\overset{.}{\beta}}_{h} = {{\overset{.}{\Psi} - \frac{S_{h} \cdot l_{v}}{m \cdot v_{x} \cdot l_{v}} - \frac{l_{h} \cdot S_{h}}{l_{v} \cdot m \cdot v_{x}}} = {\overset{.}{\Psi} - \frac{L \cdot S_{h}}{m \cdot v_{x} \cdot l_{v}}}}} & (13)\end{matrix}$from which the following relationship follows directly for the lateralforce S_(h)(α_(h)) at the rear axle $\begin{matrix}{{S_{h}(\alpha)} = {\frac{l_{v} \cdot m \cdot v_{x}}{L} \cdot \left( {\overset{.}{\Psi} - {\overset{.}{\beta}}_{h}} \right)}} & \left( 10^{''} \right)\end{matrix}$which with the desired value {dot over (β)}_(hsoll) output for thesideslip angle control at the rear axle of the reference modelcorresponds to the relationship (10′).

The {dot over (β)}_(hsoll) input required by the {dot over (β)}_(h)controller 22 for evaluating the relationship (10) or the relationship(10′) is generated by the reference model 28 and fed “directly” to thecontroller 22, as illustrated schematically by the β_(hsoll) signal path56.

The system deviation e_(h)(where e_(h)=β_(hist)−β_(hsoll)) processed“multiplicatively” by the β_(h) controller 22 with the aid of thecontroller gain k₁, which is freely selectable in principle, isdetermined at the β_(h) reference point 57.

The inputs, further required by the β_(h) controller 22, for thevariable l_(v)·m·v_(x)/L and for the actual value {dot over (Ψ)}_(ist)of the yaw angular velocity are generated by the real vehicle model 37and fed “directly” to the β_(h) controller 22, as illustrated by therelevant signal paths 58 and 59.

The determination of the desired value α_(hsoll), of the slip anglea_(h) at the rear axle 26 from the desired value S_(hsoll), obtained bythe sideslip angle control at the rear axle, of the lateral force at therear axle 26 is performed in a way similar to that with reference to the{dot over (Ψ)} controller 19.

The determination of the desired value δ_(hsoll) for the rear axle steerangle to be set, i.e., the formation of the actuating signal for thisangle, is performed in accordance with the relationship $\begin{matrix}{\delta_{hsoll} = {\beta - \frac{l_{h} \cdot \overset{.}{\Psi}}{v_{x}} + {\alpha_{hsoll}.}}} & \left( 2^{\prime} \right)\end{matrix}$The inputs, still additionally required for this purpose, for thesideslip angle β at the center of gravity 23 of the vehicle as well asfor the variable l_(h)·{dot over (Ψ)}_(ist)/v_(x), may be generated bythe real vehicle model 37 and fed to the controller 22 via signal pathswhich are represented only by a single signal arrow 60, for the sake ofsimplicity of illustration.

It is clear from the outlined type of the {dot over (Ψ)} control and theβ_(h) control that the two control loops are decoupled “physically,” andthis particularly benefits the robustness of the control.

In the case of the lateral dynamics control device 10, there is alsoprovided as an alternative to driving the front axle steer angleactuator 17 with the aid of δ_(vsoll) output signals of the {dot over(Ψ)} controller 19 a drive of the front axle steer angle actuator 17with the aid of δ_(vsoll) output signals of the further controller 21,as illustrated diagrammatically by a selector switch 61.

In functional analogy with the β_(h) controller 22 provided for drivingthe rear axle steer angle actuator 18, this further controller 21 isdesigned as a sideslip angle (β_(v)) controller which, in accordancewith a controller law of the form $\begin{matrix}{S_{vsoll} = {\frac{l_{h} \cdot m \cdot v_{x}}{L} \cdot \left\lbrack {{\overset{.}{\Psi} \cdot {\overset{.}{\beta}}_{vsoll}} + {k_{2} \cdot \left( {\beta_{v} - \beta_{vsoll}} \right)}} \right\rbrack}} & (14)\end{matrix}$determines desired values for the lateral force S(α_(v)) to be built upat the front axle 24 of the vehicle 11 by actuating the steering.

The {dot over (β)}_(vsoll) input required by the B_(v) controller 21 isgenerated by the reference model 28 and fed “directly” to the β_(v)controller 21, as illustrated diagrammatically by the {dot over(β)}_(vsoll) signal path 62. The system deviation e_(v) (wheree_(v)=β_(vist)−β_(vsoll)) processed by the β_(v) controller 21 with theaid of the once again freely selectable controller gain k₂ is determinedat the β_(v) reference point 63.

The inputs, further required by the β_(v) controller 21, for thevariable l_(h)·m·v_(x)/L and for the actual value {dot over (Ψ)}_(ist)of the yaw angular velocity are generated by the real vehicle model 37and fed “directly” to the β_(v) controller, as illustrated by therelevant signal paths 64 and 59′.

The determination of desired values α_(vsoll) of the slip angle α_(v) atthe front axle 24 from the desired value S_(vsoll) of the lateral forceobtained by the sideslip angle control at the front axle is performed asexplained with the aid of the description of the controller 19.Similarly, the determination of the desired value δ_(vsoll) for thefront axle steer angle δ_(v) to be set is also described.

The {dot over (Ψ)} controller 19 and the β_(v) controller 21 aredesigned such that the reaction behavior of the vehicle 11 in anoperating mode of the lateral dynamics control device 10 in which thesetting of the front axle steer angle δ_(v) is performed by means of the{dot over (Ψ)} controller 19 differs significantly from that reactionbehavior of the vehicle when the control device 10 operates in anoperating mode in which the setting of the front axle steer angle δ_(v)is performed by means of the β_(v) controller 21. The vehicle 11 may,therefore, be set as a result of two desired modes of reaction byswitching over the selector switch 61, for example to “sports,” i.e.,moderately oversteering, and to neutral cornering behavior.

Further modes of reaction—“vehicle types”—can be realized by virtue ofthe fact that the reference model 28 can be set selectively to variousdefined types of generation of its desired value output signals.

In order to improve the quality of the control, provision is made ofdisturbance estimators which are individually assigned to the controlledvariables and whose purpose is to detect disturbances such as side wind,roadway slope, and/or different adhesion coefficients at the two sidesof the vehicle (μ-split ratios), and to take these into account duringcontrol for the purpose of disturbance compensation. Moreover, thedisturbance estimators are also intended to compensate model errorsresulting from the fact that the vehicle model can take account ofreality only approximately. In accordance with the outlined decouplingof the control loops assigned to the front wheels 12 and 13, on the onehand, and to the rear wheels 14 and 16, on the other hand, for the sakeof simplifying the illustration, only one disturbance estimator 66 forthe front axle control loop and one disturbance estimator 67 for theβ_(h) control loop are illustrated. The disturbance estimators 66 and 67are designed, in general, as models of the controlled system which areimplemented by electronic computers. The disturbance estimators receivethe same inputs, specifically, the desired value output signals of theassigned controllers 19 and 22, as the assigned controlled systems, andgenerate therefrom outputs corresponding to the controlled variables{dot over (Ψ)} and β_(h), and also generate from the comparison of theirrelevant outputs with the corresponding outputs of the vehicle model 37of the real vehicle estimated values {circumflex over (Δ)}_(v,h) for therespective disturbance, their feedback to the controller 19 or 22rendering it possible for the system deviation to be caused to vanish.

A suitable design of such a disturbance estimator which can be extendedto the further control loops may be explained in more detail on theexample of the β_(h) control loop:

The starting point for designing the estimator 67 is the relationship$\begin{matrix}{{\overset{.}{\beta}}_{h} = {\overset{.}{\Psi} - \frac{L \cdot c_{h} \cdot \alpha_{h}}{m \cdot v_{x} \cdot l_{v}} + \Delta_{h}}} & \left( 13^{\prime} \right)\end{matrix}$for the temporal change in the controlled variable β_(h), which resultswhen the lateral force S_(h) in accordance with the relationship (9) isreplaced in the relationship (13), which also corresponds to the designmodel of the controller 22, by the relationshipS _(h) =c _(h) ·α _(h)  (9)where Δ_(h) is used to denote a deviation from the model relationship(13) which is determined, inter alia, by the linearization of thelateral force S_(h).

It is assumed for this disturbance Δ_(h) with reference to the estimatormodel that it is quasi-constant in time, that is to say that it holdsthat: $\begin{matrix}{{\overset{.}{\Delta}}_{h} = {o.}} & \left( 13^{''} \right)\end{matrix}$

Starting from this model, the disturbance estimator 67 is designed inaccordance with the relationships $\begin{matrix}{{\overset{\overset{.}{\hat{}}}{\beta}}_{h} = {{\hat{\Delta}}_{h} + \overset{.}{\Psi} - \frac{L \cdot c_{h} \cdot \alpha_{h}}{m \cdot v_{x} \cdot l_{v}} + {{k \cdot \left( {\beta_{hist} - {\hat{\beta}}_{h}} \right)}\quad{and}}}} & (14) \\{{\overset{\overset{.}{\hat{}}}{\Delta}}_{h} = {k^{\prime} - {\left( {\beta_{hist} - {\hat{\beta}}_{h}} \right).}}} & (15)\end{matrix}$

Here, in the relationship (14) k denotes a gain with which thedifference β_(hist)−{overscore (β)}_(h) is fed back into the estimatormodel represented by the relationship (13′), and k′ denotes the gainwith which the difference is fed back to the model of disturbancerepresented by the relationship (13″).

The gains k and k′ can be determined by pole prescription using theknown root locus method. The actual value β_(hist) is available asoutput of the real vehicle.

Numerical integration of the relationships (14) and (15) using knownmethods, for example the Euler method or the Runge-Kutta method, yieldsthe sought disturbance {circumflex over (Δ)}_(h), which is taken intoaccount for the purpose of balancing disturbances when forming thedesired value of the rear axle steer angle δ_(hsoll) in accordance withthe relationship $\begin{matrix}{\delta_{hsoll} = {{- \beta} - \frac{l_{h} \cdot \overset{.}{\Psi}}{v_{x}} + \alpha_{hsoll} - {{\hat{\Delta}}_{h} \cdot {\frac{m \cdot l_{v} \cdot v_{x}}{L \cdot c_{h}}.}}}} & (16)\end{matrix}$

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

1. A method for controlling yaw dynamics and lateral dynamics in a roadvehicle having a first axle and a second axle comprising; determining adesired steer angle; calculating a desired front axle value signal forinput to a first controller; calculating a desired rear axle valuesignal for input to a second controller; generating a first drive signalvia said first controller for driving an electrically drivable frontsteer-angle actuator; generating a second drive signal via said secondcontroller for driving an electrically drivable rear steer-angleactuator; determining a desired value S_(vsoll) for a lateral forceS_(v) to be built up at said front axle in a control process in acontrol loop assigned to said front axle; determining for said desiredvalue S_(vsoll) a desired value δ_(vsoll) of a front axle steering angleby a relationship of a form${\delta_{vsoll} = {{- \beta} + \frac{l_{v} \cdot \overset{.}{\Psi}}{v_{x}} + \alpha_{vsoll}}},$ wherein l_(v) being a distance from a center of gravity of said vehicleto said front axle, β being a sideslip angle, {dot over (Ψ)} being a yawvelocity, α_(vsoll) being a desired value of a slip angle at said frontaxle, and V_(x) being a longitudinal speed of said road vehicle;determining a desired value S_(hsoll) for a lateral force S_(h) to bebuilt up at said rear axle in a control process by a relationship of aform$S_{hsoll} = {\frac{l_{v} \cdot m \cdot v_{x}}{L} \cdot \left\lbrack {\overset{.}{\Psi} - {\overset{.}{\beta}}_{hsoll} + {k_{1} \cdot \left( {\beta_{h} - \beta -_{hsoll}} \right)}} \right\rbrack}$ in a control loop assigned to said rear axle, wherein m being a mass ofsaid vehicle, L being a wheelbase of said vehicle, β_(hsoll) being adesired slideslip angle of said vehicle in a region of said rear axle,and β_(h) being a slideslip angle of said vehicle in said region of saidrear axle, and β_(h) being a first controller gain; and determining forsaid desired value S_(hsoll) a value of a rear axle steering angleδ_(hsoll) by a relationship of a form$\delta_{hsoll} = {{- \beta} - \frac{l_{h} \cdot \overset{.}{\Psi}}{v_{x}} + {\alpha_{hsoll}.}}$2. The method of claim 1, wherein said desired value S_(vsoll) of saidlateral force to be built up at said front axle being determined in acontrol process by a relationship of a form${S_{vsoll} = {\frac{l_{h} \cdot m \cdot v_{x}}{L} \cdot \left\lbrack {\overset{.}{\Psi} - {\overset{.}{\beta}}_{vsoll} + {k_{2} \cdot \left( {\beta_{v\quad} - \beta_{vsoll}} \right)}} \right\rbrack}},$wherein m being a mass of said vehicle, l_(h) being a distance from acenter of gravity of said vehicle to said rear axle, β_(vsoll) being adesired slideslip angle of said vehicle in a region of said front axle,β_(v) being a slideslip angle of said vehicle in said region of saidfront axle, and k₂ being a second controller gain.
 3. The method ofclaim 2, wherein said desired value α_(vsoll) of said slip angle α_(v)at said front axle being obtained from a linear relationship of a form${\delta_{vsoll} = \frac{S_{vsoll}}{C_{v}}},$ and wherein C_(v) being anestimated front wheel slip stiffness.
 4. The method of claim 2, whereinsaid desired value α_(hsoll) of said slip angle α_(h) at said rear axlebeing obtained from a linear relationship of a form${\delta_{hsoll} = \frac{S_{hsoll}}{C_{h}}},$ and wherein C_(h) being anestimated rear wheel slip stiffness.
 5. The method of claim 1, whereinsaid desired value S_(vsoll) of a lateral force to be built up at saidfront axle being determined in a control process by a relationship of aform${S_{vsoll} = {\frac{l_{h} \cdot m \cdot a_{y}}{L} + {\frac{J_{z}}{L} \cdot \left\lbrack {{\overset{¨}{\Psi}}_{soll} - {k_{s} \cdot \left( {\overset{.}{\Psi} - {\overset{.}{\Psi}}_{soll}} \right)}} \right\rbrack}}},$wherein J_(z) being a moment of inertia, {dot over (Ψ)}_(soll) being adesired yaw velocity, and k₃ being a third controller gain.
 6. Themethod of claim 5, wherein said desired value α_(vsoll) of said slipangle α_(v) at said front axle being obtained from a linear relationshipof a form ${\delta_{vsoll} = \frac{S_{vsoll}}{C_{v}}},$ and whereinC_(v) being an estimated front wheel slip stiffness.
 7. The method ofclaim 5, wherein said desired value α_(hsoll) of said slip angle α_(h)at said rear axle being obtained from a linear relationship of a form${\delta_{hsoll} = \frac{S_{hsoll}}{C_{h}}},$ and wherein C_(h) being anestimated rear wheel slip stiffness.
 8. The method of claim 1, whereinsaid desired value α_(vsoll) of said slip angle α_(v) at said front axlebeing obtained from a linear relationship of a form${\delta_{vsoll} = \frac{S_{vsoll}}{C_{v}}},$ and wherein C_(v) being anestimated front wheel slip stiffness.
 9. The method of claim 1, whereinsaid desired value αhsoll of said slip angle α_(h) at said rear axlebeing obtained from a linear relationship of a form${\delta_{hsoll} = \frac{S_{hsoll}}{C_{h}}},$ and wherein C_(h) being anestimated rear wheel slip stiffness.
 10. The method of claim 1, whereinsaid desired value S_(vsoll) of said lateral force to be built up atsaid front axle being determined in a control process by a relationshipof a form${S_{vsoll} = {\frac{l_{h} \cdot m \cdot v_{x}}{L} \cdot \left\lbrack {\overset{.}{\Psi} - {\overset{.}{\beta}}_{vsoll} + {k_{2} \cdot \left( {\beta_{v} - \beta_{vsoll}} \right)}} \right\rbrack}},$ wherein l_(h) being a distance from a center of gravity of said vehicleto said rear axle, β_(vsoll) being a desired slideslip angle of saidvehicle in a region of said front axle, β_(v) being a slideslip angle ofsaid vehicle in said region of said front axle, and k₂ being a secondcontroller gain; wherein said front steer-angle actuator is individuallyassigned to said first axle and said rear steer-angle actuator isindividually assigned to said second axle; wherein said control loopassigned to said front axle and said control loop assigned to said rearaxle are decoupled from one another; wherein said desired front axlevalue signal and said desired rear axle value signal are generated by areference model, said reference model being implemented by an electroniccomputer from a processing of at least one output signal, representing adriver's wish, from a steering element position sensor, and of a sensoroutput signal characteristic of an operating state of said vehicle. 11.An apparatus for controlling yaw dynamics and lateral dynamics in a roadvehicle having a first axle and a second axle comprising: a firststeering device for said front axle; a second steering device for saidrear axle; a first steer angle actuator for said front axle; a secondsteer angle actuator for said rear axle; and at least one lateralacceleration sensor; wherein a first control mode for a desired valueS_(vsoll) of a lateral force at said front axle being obtained from arelationship of a form${S_{vsoll} = {\frac{l_{h} \cdot m \cdot v_{x}}{L} \cdot \left\lbrack {\overset{.}{\Psi} - {\overset{.}{\beta}}_{vsoll} + {k_{2} \cdot \left( {\beta_{v} - \beta_{vsoll}} \right)}} \right\rbrack}},$ and a second control mode for said desired value S_(vsoll) beingobtained from a relationship of a form${S_{vsoll} = {\frac{l_{h} \cdot m \cdot a_{y}}{L} + {\frac{J_{z}}{L} \cdot \left\lbrack {{\overset{.}{\Psi}}_{soll} - {k_{3} \cdot \left( {\overset{.}{\Psi} - {\overset{.}{\Psi}}_{vsoll}} \right)}} \right\rbrack}}},$ wherein m being a mass of said vehicle, L being a wheelbase of saidvehicle, l_(h) being a distance from a center of gravity of said vehicleto said rear axle, β being a sideslip angle, a_(y) being a lateralacceleration, J_(z) being a moment of inertia, and V_(x) being alongitudinal speed of said road vehicle, {dot over (Ψ)} being a yawvelocity, {dot over (Ψ)}_(soll) being a desired yaw velocity, k₂ being asecond controller gain, and k₃ being a third controller gain.
 12. Anapparatus for controlling yaw dynamics and lateral dynamics in a roadvehicle having a first axle and a second axle comprising: a firststeering device for said front axle; a second steering device for saidrear axle; a first steer angle actuator for said front axle; a secondsteer angle actuator for said rear axle; and at least one lateralacceleration sensor; wherein a first control mode for a desired valueS_(vsoll) of a lateral force at said front axle being obtained from arelationship of a form${S_{vsoll} = {\frac{l_{h} \cdot m \cdot v_{x}}{L} \cdot \left\lbrack {\overset{.}{\Psi} - {\overset{.}{\beta}}_{vsoll} + {k_{2} \cdot \left( {\beta_{v} - \beta_{vsoll}} \right)}} \right\rbrack}},$ and a second control mode for said desired value S_(vsoll) beingobtained from a relationship of a form${S_{vsoll} = {\frac{l_{h} \cdot m \cdot a_{y}}{L} + {\frac{J_{z}}{L} \cdot \left\lbrack {{\overset{.}{\Psi}}_{soll} - {k_{3} \cdot \left( {\overset{.}{\Psi} - {\overset{.}{\Psi}}_{vsoll}} \right)}} \right\rbrack}}},$wherein m being a mass of said vehicle, L being a wheelbase of saidvehicle, l_(h) being a distance from a center of gravity of said vehicleto said rear axle, β being a sideslip angle, a_(y) being a lateralacceleration, J_(z) being a moment of inertia, and V_(x) being alongitudinal speed of said road vehicle, {dot over (Ψ)} being a yawvelocity, {dot over (Ψ)}_(soll) being a desired yaw velocity, k₂ being asecond controller gain, and k₃ being a third controller gain; whereinsaid first control mode and second control mode being alternativelyselectable.
 13. The apparatus of claim 12 wherein said first controlmode and said second control mode are in a first control loop; wherein adesired value S_(hsoll) for a lateral force S_(h) to be built up at saidrear axle being obtained from a relationship of a form$S_{hsoll} = {\frac{l_{v} \cdot m \cdot v_{x}}{L}.\left\lbrack {\overset{.}{\Psi} - {\overset{.}{\beta}}_{hsoll} + {k_{1} \cdot \left( {\beta_{h} - \beta -_{hsoll}} \right)}} \right\rbrack}$ in a second control loop assigned to said rear axle, wherein β_(hsoll)being a desired slideslip angle of said vehicle in a region of said rearaxle, and β_(h) being a slideslip angle of said vehicle in said regionof said rear axle, and k₁ being a first controller gain; and wherein forsaid desired value S_(hsoll) a value of a rear axle steering angleδ_(hsoll) being determined by a relationship of a form${\delta_{hsoll} = {{- \beta} - \frac{l_{h} \cdot \overset{.}{\Psi}}{v_{x}} + \alpha_{hsoll}}};$wherein said first steer-angle actuator is individually assigned to saidfront axle and said second steer-angle actuator is individually assignedto said rear axle; wherein said first control loop assigned to saidfront axle and said second control loop assigned to said rear axle aredecoupled from one another; wherein a desired front axle value signaland a desired rear axle value signal are generated by a reference model,said reference model being implemented by an electronic computer from aprocessing of at least one output signal, representing a driver's wish,from a steering element position sensor, and of a sensor output signalcharacteristic of an operating state of said vehicle.
 14. An apparatusfor controlling yaw dynamics and lateral dynamics in a road vehiclehaving a first axle and a second axle comprising: a first steeringdevice for said front axle; a second steering device for said rear axle;a first steer angle actuator for said front axle; a second steer angleactuator for said rear axle; at least one lateral acceleration sensor; areference model, wherein said reference model generating desired valuesfor a front axle steer angle δ_(v) and a rear axle steer angle δ_(h);and wherein an automatic switchover being performed from a control modein which a desired value S_(vsoll) of a lateral force at said front axlebeing determined as a function of a system deviation (β_(v)−β_(vsoll))of a sideslip angle in a region of said front axle, into a control modein which a desired value S_(vsoll) of a lateral force at said front axlebeing determined as a function of a system deviation ({dot over(Ψ)}−{dot over (Ψ)}_(soll)) of a yaw velocity when an ability of a tireto transmit lateral force being exhausted, or virtually exhausted, in anextreme range, or a rear axle steer angle actuator has failed.
 15. Anapparatus for controlling yaw dynamics and lateral dynamics in a roadvehicle having a first axle and a second axle comprising: a firststeering device for said front axle; a second steering device for saidrear axle; a first steer angle actuator for said front axle; a secondsteer angle actuator for said rear axle; and at least one lateralacceleration sensor; wherein a disturbance estimator is provided for atleast one of a plurality control loops provided for setting a front axlesteer angle δ_(y) and a rear axle steer angle δ_(h); and wherein acontroller and a disturbance estimator which are assigned to the samecontrolled variable are designed using the same design model.
 16. Amethod for controlling yaw dynamics and lateral dynamics in a roadvehicle having a first axle and a second axle comprising: determining adesired steer angle; calculating a desired front axle value signal forinput to a first controller; calculating a desired rear axle valuesignal for input to a second controller; generating a first drive signalvia said first controller for driving an electrically drivable frontsteer-angle actuator; generating a second drive signal via said secondcontroller for driving an electrically drivable rear steer-angleactuator; determining a desired value S_(vsoll) for a lateral forceS_(v) to be built up at said front axle in a control process in acontrol loop assigned to said front axle; determining a desired value ofa slip angle at said front axle α_(vsoll) from an S_(v)(α_(v))characteristic representing a dependence of said lateral force S_(v) ona slip angle α_(v) at said front axle; determining for said desiredvalue S_(vsoll) a desired value δ_(vsoll) of a front axle steering angleby a relationship of a form${\delta_{vsoll} = {{- \beta} + \frac{l_{v} \cdot \overset{.}{\Psi}}{v_{x}} + \alpha_{vsoll}}},$ wherein l_(v) being a distance from a center of gravity of said vehicleto said front axle, β being a sideslip angle, {dot over (Ψ)} being a yawvelocity, and V_(x) being a longitudinal speed of said road vehicle;determining a desired value S_(hsoll) for a lateral force S_(h) to bebuilt up at said rear axle in a control process by a relationship of aform$S_{hsoll} = {\frac{l_{v} \cdot m \cdot v_{x}}{L}.\left\lbrack {\overset{.}{\Psi} - {\overset{.}{\beta}}_{hsoll} + {k_{1} \cdot \left( {\beta_{h} - \beta -_{hsoll}} \right)}} \right\rbrack}$ in a control loop assigned to said rear axle, wherein m being a mass ofsaid vehicle, L being a wheelbase of said vehicle, β_(hsoll) being adesired slideslip angle of said vehicle in a region of said rear axle,and β_(h) being a slideslip angle of said vehicle in said region of saidrear axle, and k₁ being a first controller gain; determining a desiredvalue of a slip angle at said rear axle α_(hsoll) from an S_(h)(α_(h))characteristic representing a dependence of said lateral force S_(h) ona slip angle α_(h) at said rear axle; and determining for said desiredvalue S_(hsoll) a value of a rear axle steering angle δ_(hsoll) by arelationship of a form${\delta_{hsoll} = {{- \beta} - \frac{l_{h} \cdot \overset{.}{\Psi}}{v_{x}} + \alpha_{hsoll}}};$wherein said front steer-angle actuator is individually assigned to saidfront axle and said rear steer-angle actuator is individually assignedto said rear axle; wherein said control loop assigned to said front axleand said control loop assigned to said rear axle are decoupled from oneanother; wherein said desired front axle value signal and said desiredrear axle value signal are generated by a reference model, saidreference model being implemented by an electronic computer from aprocessing of at least one output signal, representing a driver's wish,from a steering element position sensor, and of a sensor output signalcharacteristic of an operating state of said vehicle.
 17. An apparatusfor controlling yaw dynamics and lateral dynamics in a road vehiclehaving a first axle and a second axle comprising: a first steeringdevice for said front axle; a second steering device for said rear axle;a first steer angle actuator for said front axle; a second steer angleactuator for said rear axle; and at least one lateral accelerationsensor; wherein a desired value S_(vsoll) for a lateral force S_(v) tobe built up at said front axle being determined in a control process ina first control loop assigned to said front axle; wherein a desiredvalue of a slip angle at said front axle a_(vsoll) being determined froman S_(v)(α_(v)) characteristic representing a dependence of said lateralforce S_(v) on a slip angle α_(v) at said front axle; wherein for saiddesired value S_(vsoll) a desired value δ_(vsoll) of a front axlesteering angle being determined by a relationship of a form${\delta_{vsoll} = {{- \beta} + \frac{l_{v} \cdot \overset{.}{\Psi}}{v_{x}} + \alpha_{vsoll}}},$ wherein l_(v) being a distance from a center of gravity of said vehicleto said front axle, β being a sideslip angle, {dot over (Ψ)} being a yawvelocity, and V_(x) being a longitudinal speed of said road vehicle;wherein a desired value S_(hsoll) for a lateral force S_(h) to be builtup at said rear axle being obtained from a relationship of a form$S_{hsoll} = {\frac{l_{v} \cdot m \cdot v_{x}}{L}.\left\lbrack {\overset{.}{\Psi} - {\overset{.}{\beta}}_{hsoll} + {k_{1} \cdot \left( {\beta_{h} - \beta -_{hsoll}} \right)}} \right\rbrack}$ in a second control loop assigned to said rear axle, wherein β_(hsoll)being a desired slideslip angle of said vehicle in a region of said rearaxle, and β_(h) being a slideslip angle of said vehicle in said regionof said rear axle, and k₁ being a first controller gain; wherein adesired value of a slip angle at said rear axle α_(hsoll) beingdetermined from an S_(h)(α_(h)) characteristic representing a dependenceof said lateral force S_(h) on a slip angle α_(h) at said rear axle;wherein for said desired value S_(hsoll) a value of a rear axle steeringangle δ_(hsoll) being determined by a relationship of a form${\delta_{hsoll} = {{- \beta} - \frac{l_{h} \cdot \overset{.}{\Psi}}{v_{x}} + \alpha_{hsoll}}};$wherein said first steer-angle actuator is individually assigned to saidfront axle and said second steer-angle actuator is individually assignedto said rear axle; wherein said first control loop assigned to saidfront axle and said second control loop assigned to said rear axle aredecoupled from one another; wherein a desired front axle value signaland a desired rear axle value signal are generated by a reference model,said reference model being implemented by an electronic computer from aprocessing of at least one output signal, representing a driver's wish,from a steering element position sensor, and of a sensor output signalcharacteristic of an operating state of said vehicle.